A fuel injection valve is known in the art, for example, as disclosed in the following Japanese Patent publications:    Japanese Patent Publication No. 2011-169241    Japanese Patent Publication No. 2011-169242    Japanese Patent Publication No. 2011-012670
According to the fuel injection valve disclosed in any of the above prior arts, fuel pressure in a pressure control chamber (that is, back pressure of a valve body) is controlled so that the valve body is operated to open or close an injection port. In other words, the back pressure biases the valve body in a valve closing direction. When the fuel is discharged from the pressure control chamber to decrease the back pressure, the valve body is moved in a valve opening direction. On the other hand, when the fuel is supplied into the pressure control chamber to increase the back pressure, the valve body is moved in the valve closing direction. A structure for the above operation is formed by a fixed plate 20 and a movable plate 80 shown in FIG. 12 attached to the present application.
In FIG. 12, a high pressure passage 22 for supplying high pressure fuel into a pressure control chamber 71 and a low pressure passage 23 for discharging the fuel from the pressure control chamber 71 are formed in the fixed plate 20. In addition, the fixed plate 20 has contacting surfaces 25s and 26s at its lower end surface, in which a high pressure port 22b (corresponding to an outlet port of the high pressure passage 22) and a low pressure port 23c (corresponding to an inlet port of the low pressure passage 23) are respectively formed. The movable plate 80 is brought into contact with the contacting surfaces 25s and 26s in order to close the high pressure port 22b when discharging the fuel from the pressure control chamber 71. The movable plate 80 is separated from the contacting surfaces 25s and 26s in order to open the high pressure port 22b when supplying the high pressure fuel into the pressure control chamber 71.
The inventor of the present disclosure has found out that a linking force is generated between the fixed plate 20 and the movable plate 80 in the above structure of the prior art shown in FIG. 12, when the movable plate 80 is going to be separated from the fixed plate 20. The linking force is generated due to a fact that the fuel does not easily flow from the high pressure passage 22 and/or the low pressure passage 23 into spaces between the contacting surfaces 25s and 26s of the fixed plate 20 and the movable plate 80.
When the linking force is generated, the movable plate 80 cannot be smoothly and rapidly separated from the fixed plate 20. Then, timing for opening the high pressure port 22b may be delayed and thereby a response for increasing the back pressure and moving the valve body in the valve closing direction may go down. In such a case, a valve opening time period may become longer than intended. It may cause a problem that a fuel injection amount becomes larger than a supposed value.
In addition, since the linking force is unstable, it may cause variation for the timing of opening the high pressure port 22b. As a result, it may cause variation for the fuel injection amount.
The movable plate 80 is strongly pushed to the contacting surfaces 25s and 26s, when the movable plate 80 is in contact with the fixed plate 20. Therefore, when areas of the contacting surfaces 25s and 26s are simply made smaller in order to reduce the linking force, the contacting surfaces 25s and 26s may be worn away in an unusual manner.